Micelles of the amphiphiles can cluster onto a polypeptide chain and hydrophobic interactions among the nonpolar tails stabilize any ordered conformation of the polypeptide. We hypothesize that such induced conformation is related to the helix- and beta-forming potentials of the amino acid sequence but it can be destabilized by charged residues of the polypeptide having the same sign as the amphiphiles. This is confirmed by studying the conformation of several polypeptides and proteins in acidic sodium dodecyl sulfate solution by circular dichroism. A lone charged Glu or Asp strategically located can interfere with the formation of an induced helix or beta-segment, but protonation of these acidic residues usually enhances the amount of the induced conformation. Circular dichroic study of a series of beta-endorphin analogues in cerebroside sulfate and sodium dodecyl sulfate solutions further indicates that the helical segments may be located in the middle section of this opioid peptide, which amount to 8 or 9 residues out of 31 residues. It is stipulated that the induced helical structure of beta-endorphin bound to the membrane may bring the peptide molecule to a correct geometry that fits the sites of the receptor and thereby cascades the analgesic and other biological activities.